Symbols formed by handwriting, when traced on an electronic tablet, are represented by sequences of x-y coordinate pairs. A fundamental unit of handwriting is the stroke. A stroke is considered as a sequence of points, represented by their respective x-y coordinates. Symbols, such as letters of the alphabet and numbers, are assemblages of such strokes.
Automatic systems purporting to recognize cursive script writing, or even handwritten characters, have so far met with only limited success.
For example, reference is made to U.S. Pat. No. 4,731,857 which describes a three-step procedure for the recognition of run-on handwritten characters. First, potential segmentation points are derived. Second, all combination of the segments that could reasonably be a character are sent to a character recognizer to obtain ranked choices and corresponding scores. Third, the character sequences are combined so that the best candidate word wins. The recognition algorithm is based upon a template matching technique. Each template is a fully formed character that is assumed to be representative of the writer's average manner of forming the character. An elastic matching technique is employed to determine a score of a current character relative to each template. However, this strategy is vulnerable to the extensive variability that can be observed across different writers, and the variability of a single writer at different points in time.
Reference is also made to commonly assigned U.S. Pat. No. 5,029,223 by T. Fujisaki. This patent teaches the use of a beam search technique, in conjunction with a stack that represents a search space. Stroke labels and associated scores are represented within the search space, and the beam search technique identifies a most probable stroke label as representing an input handwritten character. One or more constraint validation filters can be employed to validate paths through the search space, and to remove invalid paths.
It is an object of this invention to provide an accurate, rapid method and apparatus for recognizing words written in a cursive manner.
It is another object of this invention to provide a dynamic programming method and apparatus for recognizing words represented by cursive handwriting.
A further object of this invention is to provide a method and apparatus that operates in a parallel manner to process cursive handwriting and to compare the cursive handwriting to a vocabulary to identify a most probable word that is represented by the cursive handwriting.
Another object of this invention provides a method and apparatus that employs conditional probabilities and, operating in a parallel manner, processes cursive handwriting in cooperation with a vocabulary to identify a most probable word that is represented by the cursive handwriting.
A further object of this invention is to provide a method and apparatus that provides a beam search technique, in conjunction with hashing, to process in a rapid, parallel manner a cursive handwriting input so as to identify a most probable word that is represented by the handwriting input.